Applications for polyetherurethane (PEU) elastomers in medicine are rapidly increasing. At the same time there is unresolved controversy as to which surface chemistries are blood compatible and as to the biostability of these materials. Degradation reported to occur in vivo may lead to the formation of sites for the initiation of calcification and to the loss of tensile strength and flex life. In this renewal proposal, these controversies will be addressed. It is the central hypothesis of this program that PEU's are potentially excellent materials for cardiovascular applications. However, because of present limitations in the understanding of the structure and chemistry of these complex polymers, PEU materials unrepresentative of their ultimate properties have been evaluated and used in medical practice. The specific hypothesis for this proposal is that lower molecular weight material dominates the surface of PEU's and also causes the "apparent biodegradation" of these polymers upon extraction. The experiments to be performed are as follows. The importance of the low molecular weight material on the surface properties will be investigated by ESCA. New techniques to give any desired surface property to PEU's will be explored. The blood compatibility of these new surfaces will be evaluated by collaborators in other programs. The effect of simulated physiological environments on the biostability of PEU's will be systematically investigated with regard to their composition. We hypothesize an increase in biostability upon the removal of these uncontrolled, unwanted synthesis byproducts. The influence of these low molecular weight materials on the mechanical properties of PEU's will be investigated. Finally, the information gleaned from the above experimental programs will be used to design superior PEU materials for use in blood contacting environments.